'Ice mouse' survived Arctic cold in the age of dinosaurs
Daniel Strain, UC Boulder
Aug. 10, 2023
Paleontologists working in northern 色视频下载 have discovered a tiny fossil mammal that thrived in what may have been among the coldest conditions on Earth about 73 million years ago.
The researchers, led by Jaelyn Eberle of the University of Colorado Boulder, described the Late Cretaceous animal in in the "Journal of Systematic Palaeontology." They gave it the scientific name Sikuomys mikros色视频下载攆rom 色视频下载淪iku,色视频下载 an I帽upiaq word for 色视频下载渋ce,色视频下载 and 色视频下载渕ys色视频下载 and 色视频下载渕ikros,色视频下载 the Greek words for 色视频下载渕ouse色视频下载 and 色视频下载渓ittle.色视频下载
Scientists excavate a site called Paul色视频下载檚 Pearls, from which teeth of the newly described mammal Sikuomys mikros were found. Left to right: Patrick Druckenmiller, JP Cavigelli, and Jaelyn Eberle.
It色视频下载檚 a fitting title. While the little ice mouse wasn色视频下载檛 actually a mouse, instead belonging to a now-extinct family of mammals called Gypsonictopidae, it was certainly tiny. The furry critter may have looked a bit like a modern-day shrew and weighed an estimated 11 grams, or less than an empty aluminum soda can. It also lived year-round in northern 色视频下载, which at the time lay much farther north, above the planet色视频下载檚 Arctic Circle. There, the ice mouse likely weathered as much as four months of unending darkness in the winter and temperatures that fell below freezing.
色视频下载淭hese guys probably didn色视频下载檛 hibernate,色视频下载 said Eberle, curator of fossil vertebrates at the and professor in the . 色视频下载淭hey stayed active all year long, burrowing under leaf litter or underground and feeding on whatever they could sink their teeth into, probably insects and worms.色视频下载
She and her colleagues had to be equally tenacious to discover the fossil animals: The researchers identified the new species from only a handful of tiny teeth, each about the size of a grain of sand.
色视频下载淚 always like working at the ends of the Earth,色视频下载 Eberle said. 色视频下载淵ou never know what you色视频下载檙e going to find, but you know it色视频下载檚 going to be new.色视频下载
Those minute fossils are giving researchers a new window into ancient 色视频下载, said study co-author Patrick Druckenmiller, director of the University of 色视频下载 Museum of the North.
色视频下载淪eventy-three million years ago, northern 色视频下载 was home to an ecosystem unlike any on Earth today,色视频下载 he said. 色视频下载淚t was a polar forest teeming with dinosaurs, small mammals and birds. These animals were adapted to exist in a highly seasonal climate that included freezing winter conditions, likely snow and up to four months of complete winter darkness.色视频下载
Venturing north
Getting to the ends of the Earth isn色视频下载檛 always easy.
The researchers, including paleontologists from the University of 色视频下载 Fairbanks and Florida State University, unearthed the fossils from sediments along the banks of the Colville River色视频下载攏ot far from the Beaufort Sea on 色视频下载色视频下载檚 northern coast. The site, part of what's called the Prince Creek Formation, is so remote the team travels the 75 or so miles from Deadhorse, 色视频下载, by snowmobile or bush plane.
Crew members excavating at a site in the snow to find Cretaceous mammals along the Colville River, northern 色视频下载.
色视频下载淥ur team's research is revealing a 色视频下载楲ost world色视频下载 of Arctic-adapted animals,色视频下载 said Gregory Erickson, a co-author of the study at Florida State University. 色视频下载淧rince Creek serves as a natural test of these animal's physiology and behavior in the face of drastic seasonal climatic fluctuations.色视频下载
The late William Clemens of the University of California, Berkeley was also a co-author of the new research.
Unlike dinosaurs from the same time period, which left behind large bones, the only fossils remaining from the region色视频下载檚 mammals are a few teeth and fragments of jaws. To recover these precious specimens, the group collects buckets of dirt from the riverbanks. In the lab, the researchers wash away the mud and sort what remains under a microscope.
色视频下载淵ou look under the microscope and see this perfect little tooth,色视频下载 Eberle said. 色视频下载渋t色视频下载檚 so tiny.色视频下载
Safety underground
In the case of the ice mouse, those perfect little teeth have inspired a perfect little mystery.
For some groups of mammals on Earth, species tend to get bigger at higher latitudes and cooler climates. The ice mouse and its close cousins seem to follow the opposite pattern. Paleontologists have found related species living thousands of miles to the south that were three to five times larger than Sikuomys mikros.
Eberle suspects the ice mouse was so small because there was so little to eat during the winter in 色视频下载.
色视频下载淲e see something similar in shrews today,色视频下载 she said. 色视频下载淭he idea is that if you色视频下载檙e really small, you have lower food and energy needs.色视频下载
Sikuomys mikros may have spent the cold months in 色视频下载 underground. In the end, such a subterranean lifestyle may have been a blessing for animals like the ice mouse. Burrowing mammals may have stood a better chance of surviving the harsh conditions that followed the meteorite crash that killed the dinosaurs 66 million years ago.
ADDITIONAL CONTACTS: Marmian Grimes, 907-474-7902, mlgrimes@alaska.edu. Patrick Druckenmiller, 907-474-6989, psdruckenmiller@alaska.edu.